Spontaneously Hypertensive Rats

Previous studies demonstrate that bilateral renal denervation enhances urinary sodium excretion and delays the onset of hypertension in young (7-week-old) spontaneously hypertensive rats (SHR) maintained on ordinary laboratory chow. We interpret these data as suggesting that increased renal nerve activity in this model contributes to hypertension by causing excess sodium retention. More recent studies show that dietary NaCl supplementation increases blood pressure and peripheral sympathetic nervous system activity in NaCl-sensitive SHR (SHR-S). The present study tests the hypothesis that the renal nerves contribute to the rise in arterial pressure caused by dietary NaCl supplementation in this model. SHR-S were fed a high (8%) or basal (1%) NaCl diet beginning at age 7 weeks. Bilateral renal denervation was carried out 2 weeks after the initiation of the diets, at which time systolic blood pressure was significantly higher in the high (compared with the basal) NaCl group. Systolic blood pressure was reduced slightly less in denervated SHR-S on the high (compared with basal) NaCl diet during the following 5 weeks. Renal denervation performed 1 week before initiation of the diets attenuated the subsequent development of hypertension equally in both groups. Both renal denervation and the high NaCl diet increased «,-adrenergic receptor numbers in the kidney; renal denervation caused an approximately equal increase in otj-adrenergic receptor binding in SHR-S on high and basal NaCl diets. The high NaCl diet increased plasma noradrenaline concentration, and renal denervation lowered mean arterial pressure but did not decrease circulating catecholamlnes in either diet group. Thus, the hypotensive effect of renal denervation in SHR-S is not dependent on a reduction of peripheral sympathetic nervous system activity. These data demonstrate that the renal nerves participate in the development of hypertension in SHR-S maintained on a basal or high NaCl diet, but the renal nerves do not appear to contribute significantly to the dietary NaCl-exacerbated component of hypertension in SHR-S. (Hypertension 1989;14:184-190)